Content-Type and content-type both are identical

[Nishchit14]

Content-Type and content-type both are identical and should be considered the same header while parsing them.

For the given snippet

`curl --request POST \
      --url https://jsonplaceholder.typicode.com/posts \
      --header 'content-type: application/json' \
      --data '{ "userId": 1, "id": 1 }'`

current behavior is

{
  method: 'POST',
  header: {
    'content-typee': 'application/json',
    'Content-Type': 'application/x-www-form-urlencoded'
  },
  url: 'https://jsonplaceholder.typicode.com/posts',
  body: '{ "userId": 1, "id": 1 }'
}

Expected is

{
  method: 'POST',
  header: { 'content-type': 'application/json' },
  url: 'https://jsonplaceholder.typicode.com/posts',
  body: '{ "userId": 1, "id": 1 }'
}